Assig-nob to national aniline



Feb. 5, 192 90 I H. F. LEWIS METHOD OF PURIFYING ANTHRAQUINONE Filed Jan. 27. 1922- STEAM SUPERHEATER 5UBLIMER HOT couoens THERM OMGTER COLD CONDENSER INVENTOR.

A TTORNEY5,

i atented Feb. 5, 1192219;

Units stares rarssr"rics,

HARRY F. LEWIS, 0]? MOUNT VERNON, IOWA, ASSIG-NOR TO NATIONAL ANILINE 8c CHEMICAL COMPANY, INC., 015 NEW YORK, N. Y., A CORPORATION OF NEW YGBK.

METHQD OF PURTFYING ANTHBAQUINONE.

Application filed January 2?, 1922. Serial No. 532,099.

This invention relates. to an improved method of. subhmmg and purifying substances that are subhmable with steam, and

more particularly to the purification of anthraquinone whereby the anthraquinone can be obtained in a state of high purity.

According to the present invention, the

crude anthraquinone is subjected to sublimation with superheated steam, and the Va pors of anthraquinone and other volatile or sublimable constituents are subjected to a regulated cooling operation by passing the vapors first through a hot condenser, maintained at a regulated temperature, and then through a relatively cold condenser at low temperature. The process is carried out with utilization of thejsuperh'eate'd steam in a particularly advantageous manner.

Among the advantages which the invention presents may be mentioned the absence of'danger of explosion, the ease of regulation of the temperature, the economy in the utilization of the, steam, and the avoidance of .the necessity of directv heating of the sublimer by a direct flame or by products of combustion.

The sublimation of the anthraquinone is V effected by heating the anthraquinone both indirectly by means of a steam acket and,

lation of the amount and temperature of the steam to obtain the desired heating effect.

The condensation of the sublimate is car-' ried out in successive stages, first at an elevat-ed temperature of aboutv 17 5-27 5 C, and later at a low temperature such that the steam itself will condense with theremaining impurities. The first or hot condenser may be preliminarily heated by steam in a steam jacket, but after it has once been ieated, the further supply of heat will be often unnecessary as the superheated steam and the sublimate will serve to reep the condenser hot, and in fact, it may be necessary to cool the condenser to a sufiicient degree t maintain it within, the proper temperature limits, for the desired hot condensation. he amount of heat which is thus made available in the'cooling of the superheated steam and in the condensation of the anthraquinone is such that often it can be utilized to advantage in preheating the steam or a part of the steam for the sublimation. For example, the condenser may have a steam jacket through which the steam is circulated to cool the condenser, and with resulting increase in the temperature of the steam ciroritmay be admixed with the superheated steam at a higher temperature from the jacket of the sublimer and the resulting superheated steam then used in the sublimer. In the hot condenser, maintained within proper temperature limits, the anthraquinone can be condensed without the condensation of impurities present in the vapor phase and which condense at a lower temiperature. The vaporpressure of anthraquinone in the'presence of superheated steam at a temperature between about 175 and 275 C. is very much less than the vapor pressure of the volatile impurities commonly found in crude anthraquinone manufactured, for

example, by oxidizing anthracene with a solution of chromic acid or other oxidizing agent, or by tie catalytic vapor phase oxidation of anthracene, or by the synthetic process from benzene and aluminum chleride, etc.-

-After the mixture, in the vapor phase, of superheated steam and anthraquinone, with its impurities, has passed through the hot condenser, and the anthraquinone condensed with substantial completeness, the resulting vapors are then passed to a cold condenser maintained at about ordinary room temperatures or at temperatures below the condensation temperature of the steam, so that complete condensation will take place of all the remaining vaporized constituents and including the steam itself. The handling of residual gases is thus avoided, while the completion of the condensation is facilitated.

Instead of passing the superheated steam and impurities directly to a cold condenser from the hot condenser, they may be passed through a condenser or condensers maintained at intermediate temperatures to bring "this in turn communicates through the pipe the invention, the apparatus being illustrated in vertical section and with parts in elevation. V I

Referring to the accompanying drawing, the sublimer is indicated at 1 and is provided with a steam jacket 2 and a supplemental steam jacket 3 at its upper end. The sublimer communicates through the pipe t with the hot condenser 5 having a steam jacket 6 and 7 with the cold condenser 8, provided with a cooling jacket 9. A suitable superheater 10 is provided for super-heating steam to the necessary temperature, the superheater being heated by gas burners 11 or by other suitable heating means. The steam, which may be supplied through pipe 26, enters the superheater at 12'and passes out through the pipe 13 which has a branch pipe Lat leading to the top of the steam jacket 3 twin which the steam passes through th-epipe 15 to the steam jacket 2 and thence through the pipe 17 to the inside of the sublimer where it is admitted near the bottom of the sublim'er through openings in the end of pipe 18. A branch connection 19 permits the superheated steam to enter the jacket 6 of the hot condenser to preheat it at the beginning of the process. A separate steam supply .20 is provided for admitting steam at a lower temperature to cool the hot condenser during the process. This steam is introduced at a temperature sufiiciently .low to cool thecondenser to the desired temperature,-and it will be heated to a higher temperature before it escapes at 21. The steam thus further preheated in the jacket (3 may be passed to the superheater through the pipe 22 to be further superheated, or it may be to a greater or less extent passed into the sublimer through the branch pipe in admixture with highly superheated steam from the superheater in which case a portion of the steam to the superheater may be supplied from pipe 26. Any excess of steam from steam jacket 6 can be discharged through pipe 25. Pipe 27 is a draiupipe for the steam jacket of the sublimer and pipe 28 is similarly a drainpipe for the steam jacket of thehotcondenser. ater condensed in thesejackets on starting the apparatus from the cold is advantageously drawn off through the drain pipes 27 and 28.

The cold condenser 8 may have water circulated through its jackets to cool it to a temperature suflicientto complete the condensation of the vapors, and it may have a that suitablethermometers or pyrometers are provided for ndlcating the temperature so that it may be maintained within proper limits. v v I I The operation of the apparatus and tl e practice of the process therein will be further illustrated by the following specific example. The impure anthraquinone resulting, for example, from the oxidation of anthracene with chromicv acid, is charged into the sublimer and heated therein, by the circulation of highly superheated steam through the acket and through the ant-hraquinone itself, to a temperature of about 275 to 850 C.

The same steam utilized at a higher temperature'in the jacket is advantageously used at a somewhat lower temperature n the sublimer. The vapor pressure of the anthra-- quinone and of the volatile impurities present in the crude anthraquinone is such, in the presence of superheated steam, that both the anthraquinone and its volatile impurities are subli ed and pass over with the steam into the condenser 5, whichv is kept at a temperature of from 175 to 275 C. or, in some cases, it may be keptwithin a narrower temperature range of, for example, 180 to 190 C. At such temperatures, substantially none of the steam is condensed While the anthraquinono is readily condensed without any considerable condensation of impurities, inasmuch as the vapor pressure of anthraquinone in the presence of steam between 175 and 275 C. is much less than the vapor pressure of the volatile impurities commonly present in the crude .anthraquinone. The

impurities accordingly will remain chiefly in the vapor phase and will pass out of the hot condenser 5 into the condenser S which is maintained at a temperature preferably below that of the condensation of steam and in which the stean'i will be condensed along with the im iiurities', and the condensation of the steam will ttSblSt in the complete condensation of the other materials, which will thus be obtained in a moist state.

The anthraquinone produced in the manner above described is substantially pure and can be obtained in the form of yellow needlelike crystals free from such impurities as anthracene, and acenaphtheneand c'arbazol and their oxidation products, etc., and with a melting point above 285.2- C.

loo

In the carrying out of the process I regard posited in the hot condenser in a substant-ially pure state and the anthracene and other impurities in the cold condenser which is maintained at a considerably lower temperature. I I

The purification of substances other than anthraquinone may be carried out in a similar manner, but the conditions of operation will differ somewhat in each case. For example, the process of the present invention may be used in 'a similar way and to similar advantage in the purification of other quinones or their derivatives, for example phenanthraquinone, methylanthraquinone, aminoanthraquinone, benzant-hrone, etc. It is also applicable to the purification of many iydrocarbons and their derivatives, for example, anthracenc, phenanthrene carbazole etc. 1

I claim: 1. The method of purifying crude anthraquinone which comprises heating anthraquinone to temperatures between 27 5 and 350 C. by circulating superheated steam in indir ct contact therewith and then into direct contact therewith to bring about its sublimation, and cooling the resulting vapors first at'an elevated temperature to separate anthraquinone therefrom and subsequently the remaining vapors at a lower temperature to separate other constituents.

2. The method of purifying crude anthraquinone which comprises heating anthraquinone to a temperature of about 275350 O. by circulating superheated steam in inclirect contact therewith and then into direct contact therewith to bring about its vaporization, and cooling the resulting vapors first to a temperature of about 17527 5 C. to separate anthraquinone therefrom, and then the remaining vapors to a temperature below the boiling point of water to separate other constituents therefrom.

In testimony whereof I affix my signature.

HARRY F. LEWIS. 

